The present invention relates to a self-locking circuit arrangement having an input voltage connection for applying an input voltage, an output voltage connection for providing an output voltage, a supply voltage connection for connecting a supply voltage, a first switching element having a first and a second output connection and a control connection, and also a second switching element having a first and a second output connection and a control connection.
Self-locking circuit arrangements containing thyristors are known from the prior art. These circuit arrangements provide, by way of example, protection in case a voltage becomes too high. If, by way of example, a voltage rises above a particular value, the thyristor triggers, as a result of which, with suitable circuitry, the output voltage returns to 0 volts. In this context, self-locking circuit arrangements should be understood as meaning circuit arrangements whose disconnection is intended to be irreversible, that is to say that the appliance powered thereby can continue to operate only as a result of a power supply reset or the like.
When there has been no disconnection, the output voltage of a self-locking circuit arrangement containing a thyristor is usually in the region of the supply voltage.
Against the background of this prior art, the present invention is based on the object of developing a generic self-locking circuit arrangement such that it is possible to dispense with a thyristor, and reliable, irreversible disconnection can be prompted if the input voltage drops below a predetermined value.
This object is achieved by virtue of the fact that, in the generic self-locking circuit arrangement, the first output connection of the first switching element is connected to the output voltage connection, the second output connection of the first switching element is connected to a reference-ground potential, the first output connection of the second switching element and also the control connection of the first switching element are connected to the input voltage connection, the second output connection of the second switching element is connected to the reference-ground potential, and the control connection of the second switching element is connected to the output voltage connection.
The present invention is based on the realization that a self-locking circuit arrangement can be produced simply and inexpensively by suitably interconnecting two transistors, in particular two bipolar transistors.
Preferably, the first and/or the second switching element is produced using a bipolar transistor or a field effect transistor. This makes it possible to attain the advantage that the circuit can be operated using very low driving power, since significantly less power need be applied than for triggering a thyristor.
Preferably, the circuit is designed such that the circuit arrangement can be locked by once lowering the input voltage to below a prescribable value. This circuit therefore makes it possible to ensure that a disconnection operation is initiated if another appliance""s supply voltage which is used as input voltage for the self-locking circuit arrangement drops below a prescribed value.
The use of suitable switching measures makes it possible to ensure that, when the circuit arrangement is blocked, the output voltage assumes a voltage which corresponds to the supply voltage multiplied by a factor a, where 0xe2x89xa6axe2x89xa61. The control connection of the second switching element can be provided with a voltage which corresponds to the supply voltage multiplied by a factor b, where 0xe2x89xa6bxe2x89xa61. This is preferably achieved by using a voltage divider.
Preferably, the block on the inventive circuit arrangement can be removed by briefly decoupling the supply voltage or shorting the output voltage, in particular using a switch, pushbutton switch or transistor.
Other advantageous embodiments can be found in the subclaims.